The effect of an interpolated circle on successive comparisons of size of circles were studied from two points of view, that is; (1) illusion of the concentric circle based on the trace of the standard stimulus S1, and (2) figural after-effect to comparative stimulus S2.Method: The stimuli were circles drawn on a white sheet of paper with a black line 1mm wide, and they were presented by the modified Dodge's tachistoscope. The observer judged the size of S2 which has the same size as S1 of a diameter of 30mm. D% or (S-L)/N was measured, in which S means number of “smaller” judgements and L number of “lager” judgements and N total number, The differences in D% between the experimental series and the control series in which the circle was not interpolated were computed.Results: 1) when S1 and S2 were presented on the right and left side respectively with a fixtion point in the central point, (a) we obtained result as expected from figural after-effect of an interpolated S or Si to S2 when Si was presented at the same position as S2. but (b) we couldn't find any definite finding when Si was presented at the same position as S1, (Exp. I, Table 1).2) The latter finding (b) cannot be ascribed to the experimental procedure in which ratio of judging large and small sizes to the isometric S2 to S1 is used as an amount of displacement. Similarly no definite trend was obtained with the method of complete series (Exp. II, Table 2).3) If the summation effect is possible when S1, Si and S2 are presented at the same position, we can explain the effect of Si in terms of figural after-effect of Si to S2, and we obtained affirmative results (Exp. III, Fig. 1, Table 3, 4).4) Using the procedure of simultaneous comparison similar to that used in figural after-effect, we measured directly the amount of displacement of S2. (Exp. IV, Fig. 1, Table 5, 6). The effect of figural after-effect was greater in this case than in the case of successive comparisons. It means the decreases of assimilation in Exp. III from the view of theory of assimilation (Table 7, 8).5) It was examined to what extent we can explain the previous results on time error by figural after-effect.

A review of literature indicated that either reactive inhibition or curiosity may explain the phenomenon of spontaneous alternation. A set of experiments was conducted to identify the relationship between these two drives. Six experimentally naive rhesus monkeys were used for this study. In one exepriment, if the monkeys pushed against and opened the door of a modified WGTA, they were permitted 10sec to look into the surroundings of a pink board settled behind the door. The E initiated each experimental period of 15min a day by raising the opaque screen and exposing the doors to the animals. Number of trials of looking into-behavior was recorded. In another experiment, after all the animals became not to show the curiosity of looking-into, a food reward, instead of a visual exploration incentive, was used for the test of spontaneous alternation in the same apparatus so arranged that only reactive inhibition did work. The six animals were given fifty-one trials a day for nine days. The results were:1. Curiosity in the rhesus monkeys disappeared in a relatively short term (Table 3), but it recovered in about 23 hours. Curiosity was maintained for about eight days (Table 1). Marked individual differences of curiosity were found in the monkeys (Table 2).2. The percentage of spontaneous alternation appeared relatively low in monkeys (Fig. 1). No statistically significant differences were obtained both between the nine days and between the five sessions of ten trials each. Individual differences in alternation were found (Table 5).3. Of greatest interest, however, was a significant positive correlation coefficientt between spontaneous alternation and curiosity. In addition, a factor analysis by the T technique showed that two typical factors were responsible for both of the two behaviors, although their loadings and variances were different from each other (Table 6). One factor was concave in the configuration of the loadings for the nine days, and another was convex (Fig. 2). The former was interpreted as the adaptation-to-situation factor, the latter as the investigation/or curiosity factor.No single factor represented by the concept of inhibition was found. Inhibition was supposed to affect the two factor loadings. It was also suggested that inhibition would increase as a result of the repetition of the investigatory reflex.

The purpose of this research is to examine the relationships between the displacement-effect of the inner circle of double concentric circles and their figureground reversal. The diameters of the inner circles were kept constant (40mm), while those of the outer varied (from 44 to 160mm).1) In each case the total length of time during which each area of the figures was perceived as a “figure” was measured in continuous observation, The result was that, despite considerable individual differences, to appear the average total time for the inner circle as a “figure” gradually increased with the increasing size of the outer circle. The opposite tendendy was found in the case of the annulus (the ringshaped area). Besides, the perceived size of the inner circle was almost the same as was previously found (Morinaga, 1935; Ogasawara, 1952). That is, the maximum amount of the displacement-effect was obtained when the ratio between the diameters of these two circles was about 2:3. Thus it seems difficult to find any particular correspondence between these two phenomena.2) With the same stimulus-figures, we compared the perceived size of the inner circle when appeared as a “figure” with that size when the annulus appeared as a “figure”. These different conditions gave rise to some divergent outcomes, These differences, however, were on the absolute amount and not of the relative amount of the displacement-effect.3) The perceived size of the inner circle was measured using a series of stimulus-figures of two kinds; that is, the inner circle easily perceived as a “figure” (by adding lines to the inner circle or making it a disk), and the annulus made easily seen as a “figure” by the same means. Some different tendencies of the displacement-effect were found under these two conditions These differences seem to depend mainly on the geometrical stimulus-differences produced by the two different kinds of figures.